Laney Valve Amp couple of problems (dead spring reverb + amp humming)

[monto]

Hi all, just picked up a Laney VC50 locally, all valve 2x12 combo for

[Travisaurus Rex]

I have a VC50 and the reverb is tube driven. If you bought it used it is probably a bad valve. I have the schematic I can send you. P.M. me if you want it and I will dig around and send it over. It will tell you which valve it is, I'm not sure. To be honest, I would replace all the tubes but that's just me. Unless I get it new or I know the tubes are somewhat new, I replace them. That way I know they probably won't go anytime soon. It should not hum so it might be tube related, or grounding issue.

[rushtallica]

Good point. I didn't know about the 'verb being tube driven but already was thinking bad preamp tube regarding the humming noise.

[monto]

thanks guys, just now i took all the 6 preamp valves out and then juggled them around a bit and then put them all back in (in different positions then they were in before). now the hum seems to have GONE! the reverb is definately a spring reverb box which i have taken out, it says 'ACCUTRONICS' stamped on it. i had no idea one of the valves might be for the reverb? eagertokill i will pm u for schematic thanks man .. in fact if u can remember if the red or white plug goes into the input or output of the reverb box id be grateful as i cant remember what goes where :sigh:

[monto]

just found this on the internet regarding checking reverb tanks, so im gonna try this:

 

"...if you have and know how to operate an ohm meter, you can tell pretty quickly if you have continuity through the in & out transducers without actually removing the tank from the amp. Just unplug the tank wires from the amp end (but remember which one went to which socket) and measure the resistance from the center pin to the shell of each plug. One plug should read fairly low at around 8 ohms or so and the other should read in the neighborhood of 100-1000 ohms or so. If either plug reads open circuit, chances are one or more of the tanks internal wires has broken, a transducer has opened, or the cable itself is bad or not making good contact with the tank socket...."

[strtdv]

The reverb on a VC50 is not tube driven.

 

The fact that you get a "clang" when you hit the tank means that the return part of the circuit is working. If you have a similar amp

 

Output impedance should be relatively high, input impedance should be fairly low (the DC resistance may read as low as 1 Ohm).

 

I'd check it for continuity, and I'd check the send and return RCA (phono) cables.

 

I'd also give the contacts on both the tank and the leads a good clean.

 

If the amp is a few years old and new to you I'd recommend changing all the tubes anyway.

 

 

There's a good chance the problem is either in the leads or the connection between the leads and the amp or the leads and the tank.

 

There's an article HERE that is pretty useful, although bear in mind that the Laney circuit is not the same as the Fender reverb circuit they're talking about here.

 

 

I spent a long time scratching my head about a non-functioning reverb on an ENGL screamer, and it was just bad connections.

[monto]

thanks strtdv, i set my ohms multimeter to '2K' and measured both of the ports on the reverb tank. one reads '.197' and the other reads '.027'

 

does that sound ok, im a bit clueless with this stuff to be honest... (i will check out the link u posted now thnks)

[Travisaurus Rex]

My bad, I was thinking of a different amp about the reverb.

[strtdv]

That sounds not too bad. One should be roughly 10 times the impedance of the other so is sounds OK.

 

The Accutronics tank is 4BB3C1B.

 

HERE is a schematic of the amp if you want a tech to look at it, they might find this helpful.

 

 

I'd replace the RCA/phono leads and give the connectors a good clean before I did anything else though.

 

 

(mods, I think posting the schematics should be OK since the VC50 isn't in production anymore, but feel free to take the link down if it breaks any rules)

[monto]

hi again guys just to let u know i think i fixed the problems.

 

the reverb tank: i had to resolder the TINY (i mean hair thin!!) single wires (the wires which go into the transducer itself).. it was a hell of a fight and i nearly lost several times .. but it works now. and i now notice the red and white plugs only work one way round so it didnt matter that i forgot which plug was for the input and which was for the output

 

the amp humming: as i mentioned above, i just changed the 6 small valves around and now the humming seems to be gone

 

so anyway i probably should change all of the valves at this point.. ok so things are just fine here now thanks again everyone and cheers for the schems eagertokill/strtdv!!